Is this random?I've been having similar problems with an optical mouse lately, but I've found out that it has to do with Firefox directly and/or my internet connection (seeding with 63kB/s which is close to where it has side effects) If you think this is not it post your /etc/xorg.conf and which touchpad you have - there are issues with some

If you have a "disable pad" button, I find that this causes issues when re activating the pad. Sometimes it locks the screen, other times it takes about 10-30 seconds for the pad to be activated again, at least on my HP dv6618eo.

You're not drunk if you can lie on the floor without holding on.--Dean Martin